High Speed Downlink Package Access (HSDPA) is an important characteristic of Version R5 of the Wideband Code Division Multiple Access (WCDMA) technique. Through a series of critical techniques including adaptive modulation and encoding, hybrid automatic retransmission, and fast dispatching by a base station, a downlink high speed data transmission is realized, and further, a downlink throughput rate of a cell is increased. Different from Dedicated CHannel (DCH) in Version R99 that resources of a cell are exclusively occupied by DCH service, the HSDPA service improves the utilization rate of resources of a cell through share of High Speed Physical Downlink Shared CHannel (HS-PDSCH), High Speed Shared Control CHannel (HS-SCCH) and power in a cell.
As a service carried in the HSDPA manner, the data service has a discontinuous transmission characteristic. The base station (NodeB) performs flow controls for the IUB-interface, so as to ensure that a user can obtain a corresponding IUB-interface bandwidth when the user requires a data transmission. In one NodeB, it is needed to further ensure that a sum of the IUB-interface bandwidth occupied by all the users does not exceed a total available IUB-interface bandwidth of the NodeB, that is, through an effective flow control manner, the total IUB-interface bandwidth of the NodeB can be sufficiently utilized.
However, in the actual network, the transmission cost of an IUB-interface is usually relatively high, and in order to save the cost, the IUB-interface bandwidth offered by the operator is always limited. Therefore, the IUB-interface resource usually becomes a bottle neck, and as a result, the available IUB-interface resources of the NodeB cannot satisfy the bandwidth demand of all the users. Thus, during the flow control for the IUB-interface, the following conflict may occur. If the NodeB allocates a large bandwidth to a radio network controller (RNC) when performing flow control for the IUB-interface in order to improve the utilization rate of the IUB-interface resources, it may cause that a sum of the IUB-interface bandwidth allocated to all the users in the NodeB is greater than the practical available bandwidth of the NodeB, that is, the so-called congestion occurs at the IUB-interface. In this case, when a user's data is delivered from the RNC to the NodeB, the data may be discarded, resulting in the data loss. This part of data can only be compensated by the retransmission at the radio link control (RLC) layer, so that the user rate is decreased, and the service quality is deteriorated. In contrast, if it is inclined to ensure the reliability of the data transmission, a conservative strategy needs to be adopted when the NodeB performs flow control for the IUB-interface, so as to ensure that congestion will not occur at the IUB-interface, but the precious IUB-interface bandwidth resources cannot be sufficiently utilized.
The essential reason for the above circumstance lies in the data transmission burst of the data service, and thus it is difficult for the NodeB to accurately control the real bandwidth required by each user at any moment. The HSDPA service is different from the DCH service of Version R99 in which the IUB-interface bandwidth allocation of the DCH service adopts a static manner, which is statically allocating the IUB-interface bandwidth according to the requested rate. In the HSDPA service, the NodeB instructs the RNC to deliver the data according to a certain bandwidth for each queue through a capacity allocation frame manner. Since it takes time to send the capacity allocation frame from the NodeB to the RNC and to deliver the data by the RNC according to the received frame, the NodeB cannot accurately predict the congestion conditions at the IUB-interface at all. In addition, as the services are established and deleted at random, and the changes of the establishment and deletion of the services may result in a variation of the total available IUB-interface bandwidth of the HSDPA service, it further takes some time for a flow control entity of the IUB-interface of the NodeB to make a response to the variation. Finally, when the NodeB sends the capacity allocation frame to the RNC, the IUB-interface bandwidth is defined by three parameters, and the values of the three parameters can only be integers, as a result, certain errors in obtaining the integers are inevitable. The above factors produce obstacles for the NodeB to perform flow control for the IUB-interface.
According to the method in the prior art, when the NodeB performs flow control for the IUB-interface, a part of the practical IUB-interface bandwidth available to the HSDPA users is reserved. Here, it is assumed that the practical IUB-interface bandwidth available to the HSDPA users is a value of A, and the reserved bandwidth is a value of B. When flow control is performed for the IUB-interface, the IUB-interface bandwidth is allocated to each HSDPA user according to the value of A-B. In this manner, a bandwidth allocation margin of the IUB-interface at a capacity of B exists, effectively preventing congestion from occurring at the IUB-interface. The greater the value of B is, the lower the probability that congestion occurs at the IUB-interface is.
Although the above method can effectively prevent the congestion from occurring at the IUB-interface, the utilization rate of the IUB-interface is directly decreased, and as a result, the precious IUB-interface bandwidth resources cannot be sufficiently utilized.